When you should resize an image
Resizing is one of the most common image-prep tasks. Three scenarios cover most of the work: your image is larger than the destination needs and you want to shrink the file (web thumbnails, email attachments, social posts that have a hard pixel cap); your image is from a screenshot or high-resolution camera and you need to match a target layout's exact dimensions (a 1500×500 banner, a 1080×1920 Reel); or you're prepping multiple variants of the same image for responsive web delivery (a single hero image at 640w, 1024w, 1920w, 2560w).
Downscaling is essentially free of quality cost — the algorithm samples groups of source pixels and writes an averaged result, which always looks crisp. Upscaling, on the other hand, can't add real detail — the algorithm guesses what's between existing pixels.
How the resampling actually works
Under the hood, the tool relies on your browser's canvas resampler — most modern browsers use a high-quality bilinear or bicubic algorithm when you set imageSmoothingQuality = "high", which this tool does. The result is comparable to what Photoshop's default "Bicubic Automatic" produces. It's not Lanczos or Mitchell — but for most practical resizes the difference is invisible to the eye.
If you need a deliberately pixelated nearest-neighbor result — for example, scaling up a pixel-art sprite — this is not the right tool. Use a dedicated pixel-art scaler that exposes nearest-neighbor as an option.
How to use this tool
- Drop a PNG, JPG, or WebP image onto the drop zone above.
- The width and height fields are pre-filled with the original dimensions. Edit either field — the other updates automatically to keep the aspect ratio.
- Click the lock icon to unlock the aspect ratio if you want to deliberately stretch or squash.
- Click Resize & download. The result is saved in the same format as your input (PNG stays PNG, JPG stays JPG, WebP stays WebP).
Practical pixel dimensions for common targets
Useful reference for common output sizes:
- Web hero image: 1920×1080 px (Full HD) or 2560×1440 px for retina displays.
- Email banner: 600 px wide max — many email clients clip wider images.
- Instagram feed: 1080×1080 (1:1), 1080×1350 (4:5), 1080×566 (1.91:1).
- TikTok / Reels / Shorts: 1080×1920 px vertical.
- YouTube thumbnail: 1280×720 px.
- App store icon: 1024×1024 px (master), then export various smaller sizes.
For more platform-specific specs, see our social media video specs reference for sizing standards across TikTok, Reels, Shorts, X, and LinkedIn.